G. Gabert: Integration or LANDSAT TM Data and SPOT Digital Elevation Model
171
geo-databases: topographical, hydrological, geological, tectonic and
geo- hazard data
environmental databases: land-use, population density, land accessibility,
road and trail data
remote sensing databases: LANDSAT TM, SPOT panchromatic and
stereo.
2.1 Application of Geoscience Data
The main data sources were ICIMOD (International Centre for Integrated
Mountain Development), DMG (Department of Mines and Geology, HMG Nepal),
E.N.S. (Ecole Normale Superieure, France), ISTAR (Imagerie Stereo Appliquee au
Relief, France), BGR (Federal Institute for Geosciences and Natural Resources,
Germany). Those map data which still existed in analogue form, were digitized
and included in the MENRIS (Mountain Environment Resources Information
System) database of ICIMOD in Kathmandu.
In the laboratories of 1ST AR and G-Sat/ENS in France, a high-quality Digital
Elevation Model (DEM) of the study area was constructed from two SPOT stereoimages (Fig. I); the earth surface was sampled every 20m, and the elevation value
of each sample has an error interval of 10m. The DEM was then digitally
connected with LANDSAT TM colour composites (TM scene 141-041, B=HV1,
G=HV 4, R=HV7) and with the digitized geological data of the map compilations
of the study area. The resulting 3-dimensional geological and geomorphologic
maps facilitated the interpretation of geological problems.
The geological interpretation had to take into account that the geology and
tectonics of the study area were partly unknown and that the area is situated in a
critical geological zone: it comprises partly the northern flank of the tectonic
synclinorium of the Kathmandu Complex, and partly the southern Central
Crystalline of the High Himalaya which is the root zone of the Kathmandu
Complex. As revealed by LANDSAT TM and SPOT image evaluation, supported
by DEM interpretation and ground truth, the basal gneisses of the Kathmandu
Complex (Bimphedi Group) and the Sheopuri and Gosaikund gneisses of the
Central Crystalline merge here; a major tectonic thrust fault, the Main Central
Thrust (MCT), apparently does not separate these two geological units. This
geoscientific result is also of importance for the geotechnical problems regarding
the planned water transfer.
2.2 Application of SPOT and LANDSAT I TM Data
to civil engineering
To tackle the geotechnical problems, first of all a slope map was derived from the
DEM. Mainly in high altitudes, above 2500m, slopes exceeding 40 degrees were
detected; in the major part of the study area, the slopes average 30 degrees. At this
stage, geo-hazard data were added to the slope data like landslides and fault zones,
in order to establish a sound basis for the assessment of the risk potential of the
study area. The area belongs to the southern slope of Langtang Himal which
forms a part of the High Himalaya range at the border of Nepal and Tibet. The
landform is highly irregular with altitudes between 1500 and 5000m, comprising
narrow ridges and steeply incised, V-shaped valleys.
171
geo-databases: topographical, hydrological, geological, tectonic and
geo- hazard data
environmental databases: land-use, population density, land accessibility,
road and trail data
remote sensing databases: LANDSAT TM, SPOT panchromatic and
stereo.
2.1 Application of Geoscience Data
The main data sources were ICIMOD (International Centre for Integrated
Mountain Development), DMG (Department of Mines and Geology, HMG Nepal),
E.N.S. (Ecole Normale Superieure, France), ISTAR (Imagerie Stereo Appliquee au
Relief, France), BGR (Federal Institute for Geosciences and Natural Resources,
Germany). Those map data which still existed in analogue form, were digitized
and included in the MENRIS (Mountain Environment Resources Information
System) database of ICIMOD in Kathmandu.
In the laboratories of 1ST AR and G-Sat/ENS in France, a high-quality Digital
Elevation Model (DEM) of the study area was constructed from two SPOT stereoimages (Fig. I); the earth surface was sampled every 20m, and the elevation value
of each sample has an error interval of 10m. The DEM was then digitally
connected with LANDSAT TM colour composites (TM scene 141-041, B=HV1,
G=HV 4, R=HV7) and with the digitized geological data of the map compilations
of the study area. The resulting 3-dimensional geological and geomorphologic
maps facilitated the interpretation of geological problems.
The geological interpretation had to take into account that the geology and
tectonics of the study area were partly unknown and that the area is situated in a
critical geological zone: it comprises partly the northern flank of the tectonic
synclinorium of the Kathmandu Complex, and partly the southern Central
Crystalline of the High Himalaya which is the root zone of the Kathmandu
Complex. As revealed by LANDSAT TM and SPOT image evaluation, supported
by DEM interpretation and ground truth, the basal gneisses of the Kathmandu
Complex (Bimphedi Group) and the Sheopuri and Gosaikund gneisses of the
Central Crystalline merge here; a major tectonic thrust fault, the Main Central
Thrust (MCT), apparently does not separate these two geological units. This
geoscientific result is also of importance for the geotechnical problems regarding
the planned water transfer.
2.2 Application of SPOT and LANDSAT I TM Data
to civil engineering
To tackle the geotechnical problems, first of all a slope map was derived from the
DEM. Mainly in high altitudes, above 2500m, slopes exceeding 40 degrees were
detected; in the major part of the study area, the slopes average 30 degrees. At this
stage, geo-hazard data were added to the slope data like landslides and fault zones,
in order to establish a sound basis for the assessment of the risk potential of the
study area. The area belongs to the southern slope of Langtang Himal which
forms a part of the High Himalaya range at the border of Nepal and Tibet. The
landform is highly irregular with altitudes between 1500 and 5000m, comprising
narrow ridges and steeply incised, V-shaped valleys.